Just Why Are Some People So Darn Tall?

June 19, 1992|By Delthia Ricks Of The Sentinel Staff

It's no mystery that 7-foot-1 Shaquille O'Neal is among the giants of the world. The question is how he and other lofty people get that way.

Scientists have sought the answer ever since Austrian monk Gregor Mendel discovered how physical traits are passed from one generation to the next. That was more than 100 years ago, and he was working with peas.

What scientists now know about people falls within two fields of biology - population and molecular genetics. It explains why some folks loom over Earth, while others are too short to ride Space Mountain at Walt Disney World.

O'Neal, the LSU star in town today to visit the Orlando Magic, will soon join the stratospheric club of professional basketball players in the United States. In a country where average men are under 6 feet, the NBA's biggest stars soar 7 feet and more.

Diet can account for some of the extremes of height, but the fine points of growth, scientists say, are probably best understood in the context of genes, the molecules tucked inside the trillions of cells in each human body.

Genes, composed of DNA, bear the history of our heredity, what makes us fat or thin, nearsighted or eagle-eyed, short or tall.

''Essentially there are a lot of genes that are involved in height,'' explained geneticist Scott Erdman of the University of California at Davis. He estimates as many as 30 genes may play a role, but scientists have yet to pinpoint them.

UC-Davis scientists are among the leaders in unlocking mysteries of polygenic traits - those caused by more than one gene. Others are skin color and high blood pressure.

How those genes are expressed, however, often can be likened to a roll of the dice, Erdman said.

The tallest woman in history, according to the Guinness Book of World Records, was Zeng Jinlian of Yujiang, in China. Zeng, who was born in 1964, stood slightly over 8 feet. She died in 1982. Both of her parents were of normal height.

The genes that made Zeng tall were no freak of nature, but an expression of traits both parents apparently carried, Erdman said.

Globally, Africa has the greatest height extremes.

Pygmies of Zaire rarely exceed 4.5 feet, while the Watusi in nearby Rwanda and Burundi average 6.5 feet and often are taller.

Northern Europeans, particularly those of Scandanavian descent, also grow well above 6 feet, as do the Tehuelches Indians of Argentina.

Still, unusual height variations show up within populations and leave scientists wondering. In Ecuador, for example, Otovalo Indian women are about 4 feet tall, while the men are similar in height to other South American males.

Why? It could be, scientists say, that over the millenia, Otovalo men simply have gotten the best food.